During the later years of the flood, many people took to the water independently, taking to ships and rafts and trading with the remaining parts of the land for food. Rather than developing communities through the seizure of large facilities, these formed communities over time through accretion. Small boats might gather around an abandoned collection of flotsam, or a small failed arcology; to these would be attracted random communities living on rafts, loners who are sick of plying the seas on their stolen boat, or raiders who want a permanent base to return to. These communities will not survive unless someone can come up with an industry that will hold them together, but such industries are not impossible to create, even amongst the flotsam and jetsam that naturally accrete to such places. Perhaps it would be prostitution in a raft city near a well-plied trade route; or a group of rafts and raiders congregated around a collection of barges that are used for scrapping stolen ships and selling the parts. Maybe someone will establish a shellfish farm on a partially-submerged ship, and then turn the shells into glass that is in turn ground into lenses; or turn unwanted glass from passing traders into valuable lenses. Perhaps the raft floats near a rich fishing area, and can sell preserved fish to traders in exchange for raw materials.

Life on raft cities is harsh, and even if they have some central industry or focus these communities will always have a sense of impermanence, of being a precarious gathering of wind-tossed rubbish that will soon be washed away. Indeed, when the ocean world’s great storms hit they often are, or only those who live near the centre survive, with the rafts on the edge serving as nothing more than human barricades against the fury of the sea. If these communities want to survive they will need to attract larger ships or rebuild themselves around abandoned arcologies and flotsam; and indeed, if a better opportunity appears the raft community will rapidly disperse to take it on. The landscape of a raft city is always changing as newcomers enter and leave, ships are cut free to sink or drift away, or storms wipe out neighbourhoods. Adventurers may find that a whole city they once knew well has gone, or that people they knew have disappeared and all who knew of them have gone as well. In the shifting world of the waves, it is often impossible to know whether they have gone to the deeps, or to a better chance.

In his book, Baxter describes one of the few pieces of useful bioengineering that are of value after the flood: a type of genetically modified seaweed that hardens into a plastic-like material as it grows in seawater, and can be shaped over time to form raft-like structures. Through the use of such biotechnology, perhaps connected to an original large base such as a floating wind power farm or larger river barges, raft cities can establish a central space on which they begin to pin some hopes of permanence. A wind-farm might be jury rigged to provide power again, connected to a ship that will form the administrative centre of the new city, and the plastiweed slowly grown around it to form a kind of island, raised from the water far enough to offer opportunities for farming and shelter from the worst storms. These raft cities will then attract less secure suburbs and exurbs, boats and rafts docked together in a higgledy-piggledy fashion, neighbours who change by the week or the month. The city as a whole will be impossible to catalogue or sustain, but its core will be permanent, and as that core grows over time – or as other parts of the city form their own stable pastiweed bases – the city will slowly take on a permanent character. As the plastiweed subsumes new ships and rafts, a floating island of chaotic colours and shapes and sizes will grow into being. These cities will often be filthy, poor and dangerous, but they represent the only legacy that the original raft communities have any hope of leaving the world.

For adventurers such cities always offer opportunities. The factions within the city will always have some nasty job they need done, and there will always be individuals who have been wronged and need to find their own justice. Though unable to offer much, many of the rafts and ships in these cities hail from before the flood, and may contain relics of technology that the rafters have no use for, but which the adventurers can use or take to a place where they can repair it. A householder looking for the return of their children from hostage takers might offer the adventurers the radar equipment from their long-immobile yacht, or a radio communication set, or a night-vision camera they have not needed since they ceased roaming the ocean. The adventurers may also be able to find more exotic work, chasing old treasure maps or taking on security work for passing traders. The bars and brothels of a raft city will be full of travelers with tales to tell and jobs to share, so a good sized raft city will always have a surfeit of work for intrepid adventurers. But it will also be full of thieves and bandits, looking to steal a good ship with its weapons, or to lead the adventurers to a pirate trap. These cities also offer repair work and resupply opportunities, though they may be overpriced and unreliable, but with the distances between communities often great, adventurers may find they have no choice.

The raft cities of the flood are like the hard scrabble colonies of intergalactic frontier settings. This is where Serenity-style adventures unfold on a yacht, and where the lowest tier of adventurers and scoundrels hide out while they wait for their chance to make their fortune. Raft cities, then, are a place all players will be familiar with, and an excellent setting to start a campaign from.